1. Field of the Invention
This invention generally relates to power-driven angiographic syringes, and specifically to a plunger for such a syringe, and to a syringe and power injector system comprising same.
2. Description of the Related Art
In the field of angiography, a contrast medium of suitable indicating character (radiopacity) is introduced under pressure into coronary arteries, and the arterial network then is monitored by fluoroscopic or other visualizing means. As a result, arterial plaque deposits and/or other arterial occlusions are readily visually determined as to their size and location, so that suitable treatment methods, such as removal of the occluding material by lasing or mechanical excision, or by displacement techniques such as balloon angioplasty, may be carried out.
To effect the introduction of the contrast medium into the arterial network for angiographic study, it has been common practice to utilize injector syringes in combination with arterial catheters. The syringe may be machine-mounted in a so-called "power injector" apparatus, with the distal end of the syringe being connected to the catheter which is introduced into the arterial system to be studied.
There is disclosed in U.S. Pat. No. 4,677,980 issued Jul. 7, 1987 to D. M. Reilly, et al., an angiographic power injector featuring a rotating turret for housing multiple angiography syringes in readiness for injection. In use, the turret is selectively rotated to align an angiographic syringe with a driving mechanism of the power injector. Specifically, as is shown in FIGS. 9 and 10 of this patent, the plunger of the angiographic syringe may be configured with rearwardly extending hook members which are engaged by the head and stem portion (typically termed a "ram" in the field) of the driving mechanism.
In the plunger configuration disclosed in this patent, the hook elements on the proximal face of the plunger are diametrally opposed to one another, to form a slot therebetween through which the ram head is inserted and subsequently rotated. The head is of transversely extending character, so that it thereby engages the respective hook members. In this manner, the head and stem of the driving mechanism and the hook members are described to constitute a quick release driving connection, with the driving mechanism head fitting into the aperture formed by the hook members, and with the stem extending out from the aperture through the access slot between the hook members.
The Reilly et al. patent, at column 6, lines 24-52 thereof, describes the subsequent operation of the coupled syringe. First, the driving mechanism is forwardly translated to drive the plunger through the syringe to expel air therefrom. Next, the syringe is connected to a source of contrast media and the driving mechanism is retracted to pull the plunger back through the syringe, to draw contrast media thereinto. Finally, the driving mechanism is advanced to drive the plunger distally in the syringe and effect injection of the contrast media through a catheter attached to the syringe. The patent states that after the injection has been carried out, the driving mechanism may be disengaged from the plunger, without reversing its movement, by the simple expedient of rotating the driving mechanism 90.degree., so that the driving mechanism head extends from the aperture on either side (see FIG. 10 of the patent). Subsequent retraction of the driving mechanism results in the head and stem of the driving mechanism being withdrawn from the aperture and slot, thereby disengaging the driving mechanism from the plunger.
As a result of the foregoing configuration of the driving mechanism, and the hook members on the plunger, the risks incident to retracting the plunger through the syringe during the angioplasty procedure are said to be eliminated, and the mating hook members and driving mechanism head are said to cooperate so that the plunger can be placed in either a driven retractable state, or an undriven non-retractable state, at any time during the injection operation and at any position of the plunger, without substantial force being applied therebetween.
While the foregoing configuration of the hook members on the plunger facilitates the engagement and disengagement of the driving mechanism, without change in the position of the plunger, it also is true that the hook members themselves provide only a very small contact area for mating with the head of the driving mechanism, when the driving mechanism is in driving or retraction engagement with the hook members.
There is thus the danger that the head of the driving mechanism may disengage from contact with the hook members during operation of the syringe, so that subsequent rotation of the driving mechanism to effect disengagement actually effects re-engagement of the driving mechanism with the hook members, in turn causing retraction of the plunger, an occurrence which is specifically desired to be avoided.
The Reilly et al. patent discloses other plunger and driving mechanism constructions, e.g., as shown in FIGS. 11-21 of the patent, but all such alternative constructions are relatively more complex in construction and operation.
U.S. Pat. No. 5,007,904 issued Apr. 16, 1991 in the names of L. L. Densmore and T. A. Lindner, discloses an angiographic syringe plunger having a generally converging distal portion, and a rear face of which is provided a coupling structure which is transversely engageable by, and transversely disengageable from, a driving mechanism of a power-driven angiographic syringe. Once engaged by the driving mechanism, the plunger cannot be disengaged solely by rotation of the driving mechanism relative to the plunger in the absence of transverse translational movement of the driving mechanism and plunger relative to one another. The coupling structure disclosed in this patent includes a wall extending rearwardly from the proximal face of the plunger body and partially circumferentially thereon. The wall terminates at a proximal extremity, and a radially inwardly extending flange is joined at an outer peripheral portion thereof to the proximal extremity of the wall. In such manner, the radially inwardly extending flange and the wall form with the proximal face of the plunger a cavity transversely open to insertion of a ram head thereinto. For example, the coupling structure described in this patent may be generally C-shaped, with a continuously curved portion having an arc length not exceeding about 180.degree., and optionally provided with tangentially extending end segments respectively joined to the extremities of the continuously curved portion.
U.S. Pat. No. 4,199,695 issued Mar. 27, 1990 to Thomas A. Lindner discloses another plunger for a power-driven angiographic syringe assembly. The plunger includes a plunger body having a generally convergent distal portion and a proximal face. Laterally spaced-apart retention members are disposed on the proximal face in diametrally opposite relationship to one another, for retaining the power driving means in position once engaged with the plunger. Each of the retention members comprises a leg portion extending generally rearwardly from the proximal face and joined at a rearward part to a bridge segment laterally inwardly extending therefrom toward the other retention member, to an inner extremity, which is in spaced relationship to the corresponding inner extremity of the bridge segment of the other retention member. The inner extremities of the bridge segments thereby define a spacing accommodating transverse passage of the drive shaft therethrough. The leg portions and bridge segments of the retention members together define with the proximal face of the plunger a lateral slot accommodating transverse passage of the driving head therethrough. Transversely outwardly extending flexible, resilient flange elements are joined to the inner extremity of each of the aforementioned bridge segments and form laterally spaced-apart, transversely aligned pairs of flange elements on either side of the bridge segments, defining a transverse channel therebetween. The flange elements are shaped to define marginal portions of the transverse channel having a reduced channel width relative to a medial portion thereof. The marginal channel portions allow transverse passage of the drive shaft therethrough by deforming the flange elements bounding the marginal channel portions, so that the drive shaft thereafter is retentively held in the medial portion of the transverse channel, to accommodate free rotation of the driving mechanism relative to the plunger, without disengaging the driving mechanism from the plunger.
U.S. Pat. No. 5,383,858 issued Jan. 24, 1995 to David M. Reilly, et al. describes a front-loading injector and syringe assembly, in which the syringe is mountable on and removable from a front wall of the injector housing. The front wall of the housing has a face plate presenting a pair of slots for receiving retaining flanges on the proximal end of the syringe. The syringe thus is inserted with the proximal end flanges passing through the slots, and then the syringe is rotated to engage the flanges behind associated retaining flanges of the face plate. The syringe contains a plunger with a proximal face having hook-like elements which engage with the ram tip of the injector apparatus. The ram tip is of elongate character and passes into the slot between the hook-like members on the proximal face of the plunger, so that subsequent rotation of the syringe into locking position engages the hook-like members with the end portions of the ram tip.
It is an object of the present invention to provide an improved front-loading syringe and injector apparatus comprising same, for injection of liquid contrast media or other fluid.
It is another object of the present invention to provide a plunger which is readily engageable with the driving mechanism of a front-load power injector system, without the necessity for registration and rotational locking.
It is a further object of the present invention to provide a face plate structure accommodating such a plunger and associated angiographic syringe.
It is yet another object of the present invention to provide a plunger structure which avoids any contamination of the internal surfaces of the syringe during loading of the syringe with contrast fluid or other media to be dispensed therefrom.
Other objects and advantages of the present invention will become more fully apparent from the ensuing disclosure and appended claims.